Bidirectional photothyristor chip, light-fired coupler and solid state relay

Abstract

A channel isolation regionis formed over the entire width of an N-type silicon substrate, and photothyristors, in each of which an anode diffusion region, a P-gate diffusion region, a cathode diffusion regionare formed parallel to the channel isolation regionover almost the entire width of the N-type silicon substrate, are formed in a left-hand portionand in a right-hand portionand are wired inversely parallel. Thus, the inter-channel movement of residual holes during commutation is restrained by the channel isolation region, by which commutation failure is suppressed to improve a commutation characteristic. Further, an operating current large enough for controlling a load current of approx. 0.2 A is obtained although a chip is divided by the channel isolation region. Therefore, using this bidirectional photothyristor chip makes it possible to implement an inexpensive SSR with a main thyristor eliminated.